Geo-Bingo is a good game for getting folks to mingle.
Each cacher is given a sheet of paper with squares on it.
In each square is a statement about caching.
Examples:
Cached from a canoe
Got questioned by the law
Got injured while caching
Went night caching
etc.
The idea is to approach the other cachers, introduce yourself, and ask if they did any of the items mentioned.
If so, they initial the square and the first to have all their squares initialed, wins!